Electrolyte Density Research Articles

Bio-waste derived zero-dimensional (0D) carbon quantum dot-doped Zinc Manganese Oxide (ZnMn₂O₄) based symmetric supercapacitors with an ultra-high energy density and exceptional cycling stability in neutral electrolytes

Bio-waste derived zero-dimensional (0D) carbon quantum dot-doped Zinc Manganese Oxide (ZnMn₂O₄) based symmetric supercapacitors with an ultra-high energy density and exceptional cycling stability in neutral electrolytes

Development and validation of an electrochemical method for electrolyte density measurement and stratification assessment in lead batteries

RESUMO Este estudo apresenta o desenvolvimento e a validação de um novo método eletroquímico para medir a densidade do eletrólito e avaliar a estratificação em baterias de chumbo. A metodologia proposta baseia-se na diferença de potencial entre dois eletrodos, sendo um composto por PbO2 e o outro por Pb, ambos preparados e caracterizados através de voltametria cíclica. A formação dos eletrodos e sua morfologia foram confirmadas por difração de raios X (DRX) e microscopia eletrônica de varredura (MEV), que revelaram a presença de estruturas tridimensionais características. Os testes com soluções de eletrólito de densidade conhecida demonstraram uma excelente correlação entre a diferença de potencial medida e a densidade real do eletrólito, com uma precisão de ±0,001 g/cm3 em relação às medições realizadas com um densímetro digital portátil. A aplicação prática do método em baterias de chumbo, realizadas em uma bateria comercial de 60Ah, validou a técnica proposta, mostrando uma correlação significativa com os dados obtidos por equipamentos comerciais. A estratificação do eletrólito é uma questão crítica em baterias de chumbo, e o método desenvolvido fornece uma ferramenta eficaz e de baixo custo para monitorar este fenômeno. A técnica pode ser aplicada em diversas pesquisas para melhorar o desempenho e a durabilidade das baterias de chumbo.

SYNTHESIS OF ELECTROLYTIC TERNARY ALLOYS WITH HIGH MICROHARDNESS

Electrodeposition of electrolytic alloys consisting of metals of the iron subgroup and zirconium allows obtaining a coating with a unique combination of physical and chemical properties that cannot be achieved by other coating methods. One of the reasons limiting the use of electrolytic coatings based on such alloys is the complexity of process control process and composition forecasting. The properties of alloys of the iron subgroup containing refractory metals and their composites depend not only on the chemical composition, that is, the content of the refractory component, but also on the deposition conditions. Varying the polarization current density allows the deposition of coatings of different composition and, accordingly, different functional properties. The aim of the work was to study the influence of electrolysis parameters on the chemical composition, structure, surface morphology and physical and mechanical properties of CoNiZr ternary alloy coatings. The formation of CoNiZr ternary alloys from citrate electrolyte on the copper surface in pulse mode was studied. The influence of electrolyte pH, mixing and current density on the composition, surface morphology and current yield and microhardness of ternary electrolytic alloys of the iron and zirconium subgroup was determined. The resulting coatings are characterized by a uniformly developed surface without cracks and sufficiently high and reproducible microhardness. Based on the results of the experiments, it can be concluded that the zirconium content does not affect the microhardness of the CoNiZr coating, but depends on the conditions of electrolysis and the properties of the electrolyte. Based on the conducted studies to determine the influence of electrolysis parameters on the microhardness of electroplated coatings, it was found that the properties of ternary CoNiZr coatings depend on the pH of the electrolyte, temperature and pulse current density. The conducted studies allow us to determine the conditions for obtaining high-quality coatings with specified functional properties.

Application of dry high-energy ball-milling to increase the density and grain boundary conductivity of solid ceramic electrolytes: Li1.3Al0.3Ti1.7(PO4)3 as a case study

Application of dry high-energy ball-milling to increase the density and grain boundary conductivity of solid ceramic electrolytes: Li1.3Al0.3Ti1.7(PO4)3 as a case study

Improvement of ionic conductivity and relative density of Li6.4La3Zr1.4Ta0.6O12 electrolytes by optimization of composition and sintering aid

Introduction All-solid-state lithium metal batteries (ASSLMBs) are expected to have high energy density. Among various solid electrolytes, oxide-based solid electrolytes have attracted attention in recent years due to their higher air stability compared to sulfide-based solid electrolytes. However, oxide-based solid electrolytes exhibit lower ionic conductivity compared to sulfide-based or liquid electrolytes, leading to inferior high-rate cycle performance. Additionally, when the relative density of solid electrolytes is low, the formation of lithium dendrites through structural defects in the solid electrolyte causes short circuits. Therefore, improving the ionic conductivity and relative density of solid electrolytes is essential for enhancing the performance of oxide-based all-solid-state batteries.In our previous research, we increased the relative density of lithium lanthanum zirconium tantalate (Li6.4La3Zr1.4Ta0.6O12, LLZT) solid electrolytes to 99.3% by co-doping LLZT with alumina (Al2O3)1) and lithium tungstate (Li2WO4)2). The increase in relative density resulted in improved short-circuit resistance performance. However, the drawback of adding these sintering aids is the reduction in ionic conductivity of LLZT due to the substitution effect on the solid electrolyte. According to the paper by N. Hayashi et al., reducing the amount of lanthanum in LLZ-CaBi solid electrolytes can improve ionic conductivity and relative density3). In this study, we attempted to enhance the ionic conductivity and relative density of LLZT by reducing the amount of lanthanum in the raw materials. Experimental The Li6.4La3-xZr1.4Ta0.6O12-1.5x (x=0, 0.03, 0.06, 0.09, 0.12,0.15) powders were synthesized via solid-state synthesis method. Lithium carbonate, lanthanum oxide, zirconium oxide, and tantalum oxide were used as raw materials. The raw materials were mixed and then heated at 900°C for 12 hours to synthesize LLZT powder. During the weighing process, lithium carbonate was added in excess by 20% of the target composition to account for lithium carbonate volatilization. LLZT powder and sintering aids were mixed using a planetary ball mill, and then the powder was pressed into pellets at 98 MPa. The pellets were sintered at 1150°C for 5 hours. Next, dry polishing was conducted to adjust the thickness of LLZT to 0.8 mm, and Au blocking electrodes were sputtered on both sides of LLZT to perform AC impedance. AC impedance measurements were performed at 30°C with an applied voltage of 10 mV over a frequency range from 1 MHz to 1 Hz. Li metal electrodes (diameter 6 mm) were attached to both sides of the Au thin film on LLZT to fabricate Li-Au|LLZT|Au-Li symmetric cells to conduct short-circuit test. In the short-circuit tests, charge-discharge cycles were repeated every 30 minutes, with the current density increasing by 0.1 mA cm- 2 every 20 cycles at 60°C. Results and Discussion Table 1 shows the relative density, resistance, and ionic conductivity of as-prepared LLZT without sintering aid. Decreasing the amount of lanthanum led to improvements in both relative density and ionic conductivity. The highest relative density achieved at x=0.06 and 0.09. Additionally, at x=0.06, bulk ionic conductivity was measured at 1.12 mS, and total ionic conductivity at 0.976 mS. The low grain boundary resistance at x=0.06 is believed to be due to the reduction in voids resulting from the improved relative density. For samples with x=0.09 and above, a gradual decrease in both relative density and ionic conductivity was observed.Figure 1 depicts the XRD patterns of LLZT from 20° to 22°. Pronounced peaks of Li2ZrO3 were observed in samples with x=0.12 and x=0.15. This is believed to result from the reaction of excess lithium, zirconium, and oxygen due to the reduction in lanthanum. Previous our studies have shown that Li2ZrO3 suppresses abnormal grain growth in LLZT particles and improves relative density. Therefore, the enhancement in relative density is likely attributed to Li2ZrO3.Figure 2 shows cross-sectional SEM images of LLZT. Abnormal grain growth and voids were observed in samples with x=0 and 0.03, while samples with x=0.06 and above exhibited no abnormal grain growth, indicating that dense solid electrolytes were successfully fabricated. This is considered evidence of abnormal grain growth suppression due to the formation of Li2ZrO3.In addition to the above, the reasons for the enhancement in bulk ionic conductivity, the characteristics of LLZT (x=0.06) added sintering aids, and the results of short-circuit tests will be discussed in more detail on the poster.

Enhancing the Energy Density and Cycle Life of Li/Sulfurized Polyacrylonitrile (SPAN) Batteries

Li/sulfurized polyacrylonitrile (Li/SPAN) batteries are garnering attention for their potential in sustainable energy storage with notable advantages such as a high theoretical energy density exceeding 1000 Wh kg-1, surpassing the 750 Wh kg-1 of Li/NMC811, and being free of transition metals. The absence of transition metals addresses concerns related to their cost, scarcity, uneven distribution, and potential toxicity. However, current Li/SPAN batteries have yet to realize their full potential in terms of energy density and cycle life. This shortfall can be attributed to a lack of comprehensive understanding across various system levels, resulting in a dearth of well-directed research efforts.In this work, we conduct a thorough study of the energy density and cycle life of practical Li/SPAN cells using internally developed models. Our analysis revealed refreshed perspectives from the common consensus among the Li/SPAN battery community. Concerning energy density, we find that this output is notably influenced by SPAN voltage, electrolyte weight, and inactive weights. In addition to the conventional method of enhancing SPAN specific capacity, these parameters present fresh opportunities to boost the energy density of Li/SPAN batteries. Details about potential executive strategies and practical viability regarding each parameter are also discussed.Regarding cycle life, while the Coulombic efficiency of Li plating/stripping (Li CE) is widely recognized as a critical factor, our analysis reveals that its impact primarily lies in regulating the consumption of the electrolyte rather than that of Li metal. Therefore, controlling the chemistry of side reactions, represented by the average equivalent molecular weight (i.e., molecular weight over number of exchanged electron) and electrolyte density, emerges as a complementary approach to improve cycle life. Overall, our findings suggest that transitioning from heavy hydrofluoroether-based localized high-concentration electrolytes (LHCEs) to lightweight alkyl ether-based weakly-solvating electrolytes is beneficial for advancing Li/SPAN batteries, both in terms of energy density and cycle life.

Cross-Linked Polyamide-Integrated Argyrodite Li6PS5Cl for All-Solid-State Lithium Metal Batteries.

Lithium dendrite growth has become a significant barrier to realizing high-performance all-solid-state lithium metal batteries. Herein, an effective approach is presented to address this challenge through interphase engineering by using a cross-linked polyamide (negative electrostatic potential) that is chemically anchored to the surface of Li6PS5Cl (positive electrostatic potential). This method improves contact between electrolyte particles and strategically modifies the local electronic structure at the grain boundary. This innovation effectively suppresses lithium dendrite formation and enhances the overall interface stability. As a result, the critical current density of the Li6PS5Cl sulfide electrolyte is dramatically boosted from 0.4 to 1.6mAcm-2, representing a remarkable fourfold improvement. Moreover, Li-Li symmetric batteries demonstrate exceptional stability, enduring over 10,000 h of consistent Li+ deposition/stripping at a high areal capacity of 3mAhcm-2. Impressively Li-LiNi0.89Mn0.055Co0.055O2 full cells exhibited outstanding cycle stability and rate performance, maintaining over 80% capacity retention after 750 cycles at a demanding 1C rate. Pouch cells produced using dry-process electrodes demonstrate strong potential for commercialization. The interphase engineering strategy offers a promising solution to the persistent challenge of dendrite growth, enabling the full realization of sulfide electrolytes' capabilities in next-generation battery technologies.

Electrochemical Characteristics of Polymer Electrolyte Fuel Cells Using Pt-Ta-Co Electrocatalysts

Introduction Polymer electrolyte fuel cells need highly active and durable electrocatalysts. Our research group has developed Pt-Ta-Co-based electrocatalysts, achieving higher electrochemical performance (1,2). To evaluate and further improve cell performance using these new catalysts, this study aims to evaluate the current-voltage characteristics, various overvoltages, and potential cycle durability by varying preparation conditions of MEAs using the Pt-Ta-Co catalysts, and to clarify the materials design principles for higher power density, higher performance, and higher durability of polymer electrolyte fuel cells. Experimental A novel electrocatalyst (Pt7Ta2Co1/KB) was prepared by loading Pt-Ta-Co catalyst on Ketjenblack as a carbon support framework by using such as cobalt nitrate as precursors. MEAs with a standard Pt/C electrocatalyst (TEC10E50E, Tanaka Kikinzoku Kogyo, Japan) for the anode, and the alternative catalyst for the cathode, were prepared by spray printing (Nordson, USA). The cathode electrocatalyst layer was deposited with various ionomer and solid contents, while the other cells were prepared along with the previous conditions (1,2). The MEAs prepared were subjected to performance tests, start-stop cycle durability tests, and load cycle durability tests. Their cell performance was analyzed by overvoltage separation and subsequent microstructural observation using field-emission scanning electron microscopy (FE-SEM). Results and discussion Figure 1 shows IR-free cell voltage of MEAs with the new Pt-Ta-Co electrocatalyst under operating conditions of 80°C, 100% relative humidity, and 1.5 bar. In the preparation of the cathode electrocatalyst layer using the new electrocatalyst, it was found that high current-voltage characteristics were obtained at the solid content of 3.5 wt.% and the ionomer-to-carbon ratio (I/C) of 1.2. As shown in Figure 1, in the low current density region, IR-free cell voltage is about 0.83 V at 0.2 A cm-2, and in the low current density region, about 0.51 V at 3 A cm-2. These electrocatalysts were highly active on the half-cell level and its single cell performance was also superior to that using the standard Pt/C (TEC10E50E) for both electrodes.As shown in Figures 2 and 3, the ECSA retention in the load cycle tests and the start-stop cycle test was higher than that of the Pt/C (TEC10E50E), suggesting that the addition of Ta contributes to suppressing the degradation of the electrocatalyst layer.In the future, we will optimize various fabrication conditions such as the ratio of water to ethanol solvent during MEA fabrication to further improve the cell performance. We will also evaluate the cell performance of new electrocatalysts with different catalyst compositions. Acknowledgments This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References T. Ogawa, Y. Inoue, K. Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara, Hayashi, and K. Sasaki, ECS Trans., 109 (9), 241 (2022).R. Miyamoto, T. Ogawa, R. Nishiizumi, M. Yasutake, Z. Noda, M. Nishihara, J. Matsuda, M. Nishihara, Hayashi, and K. Sasaki, ECS Trans., 112 (4), 353 (2023). Figure 1

Theoretical Analysis of Carbon Deposition in the Fuel Electrode of a Reversible Solid Oxide Cell

In this presentation, we aim at analyzing the changes of Gibbs free energy of carbon deposition reactions in a reversible solid oxide cell (RSOC) that utilizes a mixture of CO and CO2 in its fuel electrode compartment, operating either in fuel cell or electrolysis mode. The thermodynamics analysis was carried out by using oxygen chemical potential at the interface between the electrolyte and fuel electrode, µO2 FE|EL , and a 1-dimensional model is established to calculate µO2 FE|EL . From the thermodynamic calculation, we find that the higher µO2 FE|EL , the greater the Gibbs free energy. The change of Gibbs free energy of two possible carbon deposition reactions: CO electroreduction reaction and Boudouard reaction, are compared. Gibbs free energy changes of CO reduction reaction are evaluated based on different RSOC cell parameters as well as operating conditions, including cell voltage, current density, electrolyte thickness, electronic and ionic conductivity of electrolyte and electrodes interfaces. In this research we found that: CO can still be electrochemically reduced even the Boudouard reaction is absent in the fuel electrode. Therefore, suppressing CO electrochemical reduction reaction is critical to eliminate carbon deposition in RSOC.The RSOC is prone to carbon deposition under high cell voltages . Therefore, carbon deposition tends to occur in electrolysis mode rather than in fuel cells mode when CO concentration and cell parameters are the same. High CO concentration in the fuel mixture also facilitates carbon deposition.A thin electrolyte layer significantly increases oxygen chemical potential µO2 FE|EL at the interface of fuel electrode and electrolyte thus fabricating thin electrolyte is critical for eliminating carbon deposition. What is more, carbon deposition can be suppressed with an electrolyte exhibiting a high electronic conductivity σe EL and/or a low low ionic conductivity σi EL , indicating that increasing σe EL by doping elements such as Ce into YSZ electrolyte can help prevent carbon deposition.Modifying the interfacial area specific electronic resistance re FE|EL and ionic resistance ri FE|EL across fuel electrode and electrolyte also contribute to carbon deposition prevention. Increasing re FE|EL or reducing ri FE|EL is beneficial to suppress carbon deposition.Contrary to the the interface between fuel electrode and electrolyte, low interfacial area specific electronic resistance re OE|EL and high interfacial area specific ionic resistance ri OE|EL is in favor of suppressing carbon deposition. However, a relatively lower ri OE|EL is also required to obtain an outstanding RSOC electrochemical performance.

Moss-like Growth of Metal Electrodes: On the Role of Competing Faradaic Reactions and Fast Charging

Uncontrolled crystal growth during electroreduction of reactive metals in liquid electrolytes produces mossy metal deposits. Here we use electroanalytical Rotating-Disk Electrode (RDE) studies to elucidate the origin of moss-like growth of metals. We report that competing Faradaic reactions occurring on the electrode surface is the source of the phenomenon. A moss-like growth regime can be accessed by subtle shifts in electrolyte chemistry and deposition rate. Specifically, for Zn—a metal that conventionally is not known to form moss-like electrodeposits—obvious moss-like patterns emerge at low-current densities in strongly-alkaline electrolytes that undergo electroreduction to form an interphase. Conversely, under conditions where the rate of metal electroplating is large relative to that of other competing Faradaic reactions, it is possible to eliminate the moss-like growth. We further evaluate this principle in Li metal deposition and again find that the typical moss-like electrodeposit morphology of Li can be eliminated. As an empirical rule, an applied current density i that satisfies 10 is < i < 0.8 ilim could suppress instabilities giving rise to porous growth patterns. Our findings open up a new approach for achieving favorable metal deposition morphology and fast charging in next-generation batteries.

High Energy Density Sulfide-Based All-Solid-State Batteries by Tailoring Electronic Conductivity within Composite Cathode

The sulfide-based all-solid-state batteries (ASSBs) has guaranteed having excellent safety by using non-combustible inorganic solid-electrolyte (SE). SE separator can transport Li ion selectively and there is no concentration gradient in theory, enabling fast charging. In addition, due to high ionic conductivity of sulfide-based SE comparable to liquid based electrolyte, high capacity and high energy density ASSBs of 5mAh cm-2 have been developed to a stage close to commercialization.So far, among the many issues of ASSBs, the performance improvement has been achieved by focusing on interfacial deterioration issues. However, recent several studies have analyzed and identified the cause of inhomogeneous reaction in composite cathode, which lead to capacity degradation quickly. It had been confirmed that the inhomogeneous reaction was caused by not only loosely contact and isolated active materials but also restriction Li conductivity in nano-crystal boundaries of active materials, resulting in localizing overcharge-discharge and decreasing in capacity and rate capability. As one of intrinsic properties of ASSBs, the solid-solid contact induce the limitation of lithium ion mobility and it also triggered insufficient electronic conduction pathway increasing charge transfer resistance.In order to develop high-energy density and high power ASSB, the ability of the conductivity for electron and ion must be balanced through the formation of a well-developed electronic percolating pathway. In this study, the inhomogeneous reactivity that can be maximized in thick electrodes is alleviated by improving the electron transfer path in the composite cathode. To uniformly transfer electrons in the composite cathode, we introduced argyrodite type SE coating with 2D conductive material under solvent environment. This approach is effective on forming a continuous electronic pathway for homogeneous reactivity as well as reduce SE oxidation by preventing direct contact between SE and cathode active material. As a result, we obtained a high initial capacity of 206 mAh g-1 using a single LiNi0.8Co0.1Mn0.1O2 cathode and SE coated with 2D conductive material, and confirmed that approximately 90% rapacity maintained after 200th cycle.

The Modulation of Cross-Linking Density in Gel Polymer Electrolyte for the Inhibition of Lithium Dendrite

The Modulation of Cross-Linking Density in Gel Polymer Electrolyte for the Inhibition of Lithium Dendrite

An insight into synergistic effect of polyaniline and noble metal (Ag) on vanadium pentoxide nanorods for enhanced energe storage performance

The widespread applications of vanadium pentoxide (V2O5) are limited because of its low electrical conductivity and restricted ion diffusion coefficient. To address these constraints, the present study includes a straightforward and effective approach for fabricating polyaniline based silver-decorated vanadium pentoxide (Ag–V2O5/PANi) as an electrode material. The structural and morphological investigation of prepared electrode materials were made by X-ray diffraction analysis and scanning electron microscopy respectively. In comparison to pure Ag–V2O5, the Ag–V2O5/PANi composite demonstrated enhanced performance in various aspects. Specifically, the Ag–V2O5/PANi showed a higher specific capacitance (628 Fg−1) when subjected to a current density (1 Ag−1) in KOH electrolyte. Additionally, it has an energy density of 153 Whkg−1. Furthermore, the Ag–V2O5/PANi composite exhibited superior stability even after undergoing 3000 charge to discharge cycles. Exceptional capabilities shown can be ascribed to synergistic interaction between PANi and Ag–V2O5. The remarkable outcomes obtained from these electrode materials have the potential to foster novel prospects in high-energy-density storage systems.

Mild and rapid construction of Ti electrodes for efficient and corrosion-resistant oxidative catalysis at industrial-grade intensity

The development of cost-effective and corrosion-resistant catalytic electrodes for chlorine/oxygen evolution reaction (CER/OER) in large-scale industrial applications is a significant challenge. Herein, the sol–gel method is employed to achieve a uniform coating of ruthenium (Ru) doping copper (Cu) on titanium sheet (Ru + 20 %Cu@Ti), and the highly efficient industrial grade stable Ti dimensional stable anode can be quickly constructed at 723.15 K for 2 h. Cu doping reduces the vacancy formation energy of surface oxygen, promotes additional lattice oxygen vacancy assisted hydrolysis dissociation pathway, improves the selectivity and specific activity of CER at high concentration doping, and reduces the binding energy of OER intermediates (e.g., *OH, *O, and *OOH) at adjacent Ru active sites. The overpotentials require to reach the current density of 10 mA cm−2 for CER and OER were only 365 mV and 232 mV at the conditions of 5.0 M NaCl (pH = 7.0) and 1.0 M KOH + 0.5 M NaCl. More importantly, Ru + 20 %Cu@Ti demonstrates excellent stability, operates continuously for over 340h at industrial current density in neutral and alkaline electrolytes, and its strengthening life reaches 64 h, with ultra-low performance attenuation. Impressively, the designed applied electrode (8.0 cm ✕ 15.0 cm) achieves long-term CER at 0.2–0.3 A cm−2. Further industrial grade evaluation of CER shows that its chlorine extraction polarizability, enhances life and weight loss meet the requirements of industrial applications.

Revealing the intricacies of natural convection: A key factor in aqueous zinc battery design

Aqueous zinc-based batteries offer high safety, abundant resources, low cost, and environmental friendliness, making them a promising alternative to lithium-ion batteries for large-scale energy storage markets. However, the natural convection in the electrolyte during operation, which can greatly affect the battery performance, is overlooked for a long time. Through particle tracing experiments, this study demonstrates that in the vertical placement of the battery, natural convection occurs due to the variation of electrolyte density, whereas it does not happen when the cathode is on top. Besides, there is a significant difference in electrochemical performance between these two configurations, with a voltage difference of up to 0.25 V at 10 mA cm⁻² and a peak current difference of up to 3.4 mA in linear sweep voltammetry. Simulation results show that convective mass transfer can be up to 100 times greater than diffusive mass transfer in a bulk solution. This highlights the importance of considering natural convection to improve model accuracy. Further, to increase energy density, batteries are scaled up in practical applications to reduce the weight of the casing. This work simulates mass transfer conditions under various scenarios, illustrating the trade-off between current density and battery size, and offering new guidance for the design of aqueous zinc-based batteries.

Constructing Donor–Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li+ Migration in Quasi-Solid-State Battery

HighlightsDonor–acceptor-linked covalent organic framework (COF)-based electrolyte can not only fulfill highly-selective Li+ conduction, but also offer a crucial opportunity to understand the role of electronic density in quasi-solid-state Li metal batteries.Donor–acceptor-linked COF electrolyte results in Li+ transference number 0.83, high ionic conductivity 6.7 × 10–4 S cm−1 and excellent cyclic ability in Li metal batteries.In situ characterizations, density functional theory calculation and time-of-flight secondary ion mass spectrometry are adopted to expound the mechanism of the rapid migration of Li+ in the “donor–acceptor” electrolyte system.

Hydrogen production from ZnCl2 salt: Application of chlor-alkali method

This experimental study investigates the efficiency of hydrogen production from an aqueous ZnCl2 solution using an electrochemical method within a chlor-alkali reactor. A laboratory-scale reactor with separate anode and cathode compartments was constructed for this purpose. The compartments are separated by a Nafion 212 membrane, which prevents the mixing of the anolyte and catholyte solutions while allowing the passage of positive ions (Zn+). Each compartment is equipped with five carbon rod electrodes. The anode chamber is fed with an aqueous ZnCl2 solution, while the cathode chamber is supplied with pure water. The experiments were conducted with a constant electrolyte transfer rate of 0.3g/s into the reactor, at three different cell voltages (5.0, 7.5, and 10.0V) and two different cell temperatures (20 °C and 45 °C). Due to the small reactor dimensions and the dilution effect caused by adding pure water to the cathode compartment which decreases electrolyte density and adversely affects the current a noticeable reduction in hydrogen gas production was observed. Furthermore, the ZnCl2 electrolyte mass flow rate did not significantly impact the current or the generation of hydrogen and chlorine gases. Consequently, no changes were made to the mass flow rate of pure water or the electrolyte. The presence of active chlorine gas was found to cause the erosion of the carbon rod electrodes in the anode chamber. As a result, the amount of chlorine gas produced in the anode chamber is significantly lower than the hydrogen gas produced in the cathode chamber. At a cell temperature of 20 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 5 V with ZnCl2 aqueous solution, the minimum hydrogen production rate is 0.625 mL/min. In contrast, at a cell temperature of 45 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 10 V, the maximum hydrogen production rate is 4.97 mL/min.

Determining the required amount of added solvent (H2O) to obtain a given electrolyte density

Problem. The article proposes a method for determining the required amount of water that must be added to obtain a given density of the electrolyte. Goal. The method of calculating the volume and mass of water necessary for diluting the electrolyte solution to a given density is considered. Methodology. This calculation allows, if necessary, to check the obtained results of measurements of the concentration of the electrolyte and to calculate the given density of the electrolyte taking into account the addition of the solvent (H2O). With periodic dosed replenishment of water consumed from the electrolyte, the electrolysis process occurs at a variable concentration of alkali in the electrolyte. Results. The proposed dependencies and the calculation method developed on their basis make it possible to increase the efficiency of the electrolysis process by reducing energy costs due to ensuring optimal specific conductivity of the electrolyte at a variable concentration of alkali. Originality. The resulting calculation dependence allows both during the development and operation of operating alkaline electrolyzers to calculate the current concentration and the range of changes in the concentration of alkali in the electrolyte. Practical value. The application of the obtained dependence for alkaline electrolyzers with periodic replenishment of feed water and for developed operating electrolyzers allows to analyze the nature of changes in the specific electrical conductivity of the electrolyte, i.e. evaluate the efficiency of the electrolysis process.

Ultrasound-assisted fungal self-growth and heteroatom doping for the preparation of high-performance lignocellulose-based supercapacitor electrodes

Biomass materials are widely used as supercapacitor electrode materials due to their cost-effectiveness and eco-friendliness. In this work, ultrasound-assisted impregnation was employed for the thorough mixing of the liquid medium, and fungal treatment was conducted on the three main components of lignocellulose to prepare a fungi-modified heteroatom-doped lignocellulose-based carbon material (LCF-NP). The effects of heteroatom doping, the content of the three main components, and fungal modification on the electrochemical performance of lignocellulose-based carbon materials was investigated. The results revealed the synergistic effect of heteroatom doping and fungal treatment on the electrochemical performance. Compared with its counterpart free of fungal treatment, LCF-NP has a more reasonable pore structure and exhibits excellent electrochemical performance. LCF-NP porous carbon material has the highest specific surface area (792 m2/g), large pore volume (0.523 cm3/g), and ideal specific capacitance (1940 mF/cm2) under the conditions of 1.0 M Na2SO4 electrolyte and current density of 0.5 mA/cm2. After 10,000 cycles, there is almost no loss of capacitance. These results indicate that the joint utilization of heteroatom doping and fungal treatment has a promising application prospect in pore structure regulation and electrochemical performance improvement. This study provides a new strategy for the preparation of lignocellulose-based carbon electrode materials.

Electrochemical analysis on SnSeO3/ZnSeO3 nanocomposite

Nanocomposite SnSeO3/ZnSeO3 has been synthesized by hydrothermal method. X-ray powder diffraction confirms formation of SnSeO3/ZnSeO3 nanocomposite. It exhibits an interesting morphology of needle like nanorod structure. Thermal analysis reveals the thermal stability, decomposition behavior and critical temperatures where significant weight loss occurs. X-ray photoemission explains the role of the chemical state Sn, Zn, Se and O in SnSeO3/ZnSeO3. Electrochemical study has been made in both three electrode and two electrode system. In three electrode system, cyclic voltammetry exhibits a bell-shaped curve and the operational potential window is 0.8 V. The specific capacitance is 78.65 F/g for 5 mV scan rate. Chronopotentiometry shows quasi-triangular curves demonstrating the behavior of pseudo capacitors. Specific capacitances of 72.02 F/g was delivered at 1 A/g current density in 3M electrolyte of KOH. The plot of Nyquist for SnSeO3//ZnSeO3 confirms pseudo capacitor behavior. The series resistance Rs is low that is 0.78 Ω and charge transfer resistance is 0.42 Ω. Symmetric SnSeO3/ZnSeO3 supercapacitor device that is, two electrode system, is fabricated using 3M KOH electrolyte. Operational potential window is 1.5V. Cyclic voltammetry curves of the device show excellent capacitive behavior. The symmetric device produced specific capacitances of 39.37F/g, energy density 6.15 Wh kg-1 and power density 374.99 kW kg-1 at 1Ag-1 current density. The cell displayed 73.18% capacity retention, indicating excellent electrode stability for approximately 5000 cycles at a current density of 1 Ag-1 . Nyquist plot suggests that the system is stable and exhibits capacitive behavior.